fix: Correct DB clsuter parameter group used when users do not create one nor provide the name of existing, will use default (#320)

Author: bryantbiggs

.pre-commit-config.yaml

@@ -1,6 +1,6 @@
 repos:
   - repo: https://github.com/antonbabenko/pre-commit-terraform
-    rev: v1.74.2
+    rev: v1.75.0
     hooks:
       - id: terraform_fmt
       - id: terraform_validate

README.md

@@ -302,7 +302,7 @@ No modules.
 | <a name="input_db_cluster_instance_class"></a> [db\_cluster\_instance\_class](#input\_db\_cluster\_instance\_class) | The compute and memory capacity of each DB instance in the Multi-AZ DB cluster, for example db.m6g.xlarge. Not all DB instance classes are available in all AWS Regions, or for all database engines | `string` | `null` | no |
 | <a name="input_db_cluster_parameter_group_description"></a> [db\_cluster\_parameter\_group\_description](#input\_db\_cluster\_parameter\_group\_description) | The description of the DB cluster parameter group. Defaults to "Managed by Terraform" | `string` | `null` | no |
 | <a name="input_db_cluster_parameter_group_family"></a> [db\_cluster\_parameter\_group\_family](#input\_db\_cluster\_parameter\_group\_family) | The family of the DB cluster parameter group | `string` | `""` | no |
-| <a name="input_db_cluster_parameter_group_name"></a> [db\_cluster\_parameter\_group\_name](#input\_db\_cluster\_parameter\_group\_name) | The name of the DB cluster parameter group | `string` | `""` | no |
+| <a name="input_db_cluster_parameter_group_name"></a> [db\_cluster\_parameter\_group\_name](#input\_db\_cluster\_parameter\_group\_name) | The name of the DB cluster parameter group | `string` | `null` | no |
 | <a name="input_db_cluster_parameter_group_parameters"></a> [db\_cluster\_parameter\_group\_parameters](#input\_db\_cluster\_parameter\_group\_parameters) | A list of DB cluster parameters to apply. Note that parameters may differ from a family to an other | `list(map(string))` | `[]` | no |
 | <a name="input_db_cluster_parameter_group_use_name_prefix"></a> [db\_cluster\_parameter\_group\_use\_name\_prefix](#input\_db\_cluster\_parameter\_group\_use\_name\_prefix) | Determines whether the DB cluster parameter group name is used as a prefix | `bool` | `true` | no |
 | <a name="input_db_parameter_group_description"></a> [db\_parameter\_group\_description](#input\_db\_parameter\_group\_description) | The description of the DB parameter group. Defaults to "Managed by Terraform" | `string` | `null` | no |

main.tf

@@ -71,7 +71,7 @@ resource "aws_rds_cluster" "this" {
   copy_tags_to_snapshot               = var.copy_tags_to_snapshot
   database_name                       = var.is_primary_cluster ? var.database_name : null
   db_cluster_instance_class           = var.db_cluster_instance_class
-  db_cluster_parameter_group_name     = var.create_db_cluster_parameter_group ? aws_rds_cluster_parameter_group.this[0].id : local.cluster_parameter_group_name
+  db_cluster_parameter_group_name     = var.create_db_cluster_parameter_group ? aws_rds_cluster_parameter_group.this[0].id : var.db_cluster_parameter_group_name
   db_instance_parameter_group_name    = var.allow_major_version_upgrade ? var.db_cluster_db_instance_parameter_group_name : null
   db_subnet_group_name                = local.db_subnet_group_name
   deletion_protection                 = var.deletion_protection

variables.tf

@@ -599,7 +599,7 @@ variable "create_db_cluster_parameter_group" {
 variable "db_cluster_parameter_group_name" {
   description = "The name of the DB cluster parameter group"
   type        = string
-  default     = ""
+  default     = null
 }
 
 variable "db_cluster_parameter_group_use_name_prefix" {